VMware CBT bug KB 2090639

[Vitaliy S.]

Changing size of the datastore does not matter, so you're safe here. And yes, you should reset the CBT data and apply the hotfix to workaround this issue. Thanks!

[foggy]

...and yes, the described procedure solves the issue for both backups and replicas.

[r.mckeon]

Thank you Vitaliy and foggy

[jbrullemans]

Hi,

I hav extended a disk in a few month's ago from 350GB to 400GB. At that time i was running Veeam 7. Question 1 and i'm affected by the bug. And currently we are running Veeam V8 if i extend that disk for another 10gb is it than safe to presume that veeam will disable CBT and run a backup and than reanble it again so that i'm safe for the bug?

[foggy]

I hav extended a disk in a few month's ago from 350GB to 400GB. At that time i was running Veeam 7. Question 1 and i'm affected by the bug.

Chances are, you're affected.

And currently we are running Veeam V8 if i extend that disk for another 10gb is it than safe to presume that veeam will disable CBT and run a backup and than reanble it again so that i'm safe for the bug?

Yes (be ready for the longer job run after that).

[ashman70]

I am still confused, if a VM was created with a 200GB partition and then expanded to 250GB, is it vulnerable to this problem?
Is it only when a VM is expanded past 128GB, 256GB or 512GB that it is vulnerable to this problem?
Or does if affect all VM's greater then 128GB regardless of whether they were expanded past 128GB?

[Vitaliy S.]

Is it only when a VM is expanded past 128GB, 256GB or 512GB that it is vulnerable to this problem?

Yes, this is correct according to latest VMware edits to the KB article:

Are virtual machines grown in smaller increments affected?
The amount of space the virtual disk is extended is not relevant, the increment of space by which a virtual disk is extended is not relevant. The virtual machine has this issue when its disk is grown past any 128GB boundary in absolute size. The issue is triggered at other sizes which are a power of 2 from 128GB up. For example: 256GB, 512GB, and 1024GB.

[ashman70]

Ok so it looks like we expanded the D drive of a vm from 250GB to 300GB so I assume then that this vdisk is vulnerable to the problem.

I haven't read through many pages in this thread, what is the fix for this specific vm? I am on 5.1 update 2 running Veeam 6.5.1 build 109.

[Gostev]

Hello, KB1940 has all the information about this issue collected.

Basically, there is no solution for 6.5, as this version is no longer supported by our technical support. You need to upgrade to at least 7.0 Patch #4 and apply a hot fix from KB1940, or better yet upgrade directly to 8.0. After that, you should reset CBT on all of your VMs that may have been affected (if unsure, best is to reset CBT on all VMs).

Thanks!

[Gostev]

I will be locking this thread now. If anyone has further questions not covered in the KB article, please either read this thread (as all possible questions have been answered multiple times by now), or just contact our technical support for assistance (if this thread is too long for you to read).